twyg lets you visualise arbitrary tree structures in a pretty way. The appearance of the tree (layout, color, node, connection shapes, etc.) is fully controlled via configuration files in a generative way. This means that almost all visual properties of the output can be controlled by expressions that depend on the characteristics of the tree (e.g. the color or shape of a node can be a function of its hierarchical position in the tree). This allows for crafting very flexible configurations that can be applied to trees of arbitrary size and complexity. It supports the Cairo and NodeBox1 rendering backends.